This invention relates to electromechanical transducers and more particularly to a housing and interconnection configuration to enable operation of such a transducer in a relatively deleterious environment.
Such transducers, especially those of the piezoresistive type, have found widespread use in many varying applications. The piezoresistive transducer employs at least one silicon resistive element mounted on a diaphragm. The resistance of the piezoresistive device varies according to the intensity or magnitude of an applied force. The force is usually applied to the relatively thin diaphragm member which may be fabricated from a semiconductor or metallic material and serves to deflect or displace the diaphragm to therefore cause the resistance of the piezoresistive element to change. These devices provide a reliable output which is proportional to the magnitude of the applied force or pressure. In modern applications, such transducers have found widespread use in the automotive and other industries. In various applications, the transducers have been employed to measure such quantities as manifold pressure, exhaust pressure and various other pressures and forces which are associated with the operation of an internal combustion engine or the operation of a motor vehicle in general. As one can imagine, based on this application, one requires an extremely reliable device which is relatively inexpensive.
While the art of transducers has progressed to a point where the piezoresistive devices are extremely reliable, one has to provide a rugged housing in order to mount the device within the operating environment. In providing such a housing and in order to make the device as economical as possible, one has to assure that the assembly process is rapid and simple while maintaining reliability. In this manner, one can reduce the cost of assembly in eliminating various assembly tasks which are performed by relatively skilled labor. Due to the nature of the environment, one also has to assure that the transducer or the semiconductor device is not exposed to the various pollutions or deleterious substances which are present in the atmosphere. A major problem in the transducer art is to supply such a unit which is associated with heavy pins or posts to enable one to plug the unit into a corresponding socket or base or to affix electrical cabling. In so doing, the unit must be capable of being easily inserted and removed in numerous operations without effecting the transducer assembly. In order to solve such problems, the prior art posed many typical solutions. One approach in the prior art was to protect the surface of the transducer with a suitable organic gel or coating. Such coatings do not provide complete protection and further serve to interfere with the transducer operation and response.
The prior art also proposed many different housing configurations in an attempt to isolate the transducer from the environment, while further attempting to provide a hermetic package. Such techniques are relatively complicated in providing housings which consist of numerous parts and are difficult to fabricate and assemble. In particular, one experienced difficulty in the prior art in utilizing heavy conductors such as metal posts or pins in conjunction with a transducer assembly. In such prior art techniques, heavy conductors were either soldered to individual conductors or one utilized hybrid interconnection techniques. These approaches were not optimum in that the interconnections were mechanically weak as requiring multiple bonding techniques, while they were associated with larger resistance due to the hybrid structures. In many techniques, one employed conductive epoxies such as gold epoxies and so on which resulted in additional expense, fabrication difficulties and introudced additional contact reliability problems.
It is therefore an object of the present invention to provide an improved transducer housing, which employs heavy conductors or posts to enable the transducer to operate in conjunction with a suitable socket or base assembly.